Effects of pentobarbital and flurazepam on respiratory neurons in undrugged cats

Two hypnotic drugs known to enhance GABAergic transmission, a barbiturate (pentobarbital) and a benzodiazepine (flurazepam), were applied locally to respiratory-related neurons (RN) located in the ventral respiratory area in the medulla of non-anaesthetized cats which were either decerebrated or chronically implanted. Pentobarbital applied iontophoretically depressed the spontaneous discharge rate of most RN tested as well as the increase in firing of RN discharge induced by iontophoretic application of glutamate; pentobarbital also potentiated inhibition induced by iontophoresed GABA. Flurazepam applied by iontophoresis or pressure pulses depressed a minority of RN tested and did not enhance GABA-induced inhibition. These results suggest: (1) that inhibition of RN activity through GABAergic mechanisms can be affected by drugs which act at the chloride ionophore but not those acting indirectly through the benzodiazepine binding site, and (2) the effects of the agents on medullary neuronal activity are independent of an effect on the states of consciousness or on structures rostral to the medulla.